1.1. Technical Field
This invention relates to an improved ski goggle which is comfortable to wear, prevents goggle lens fogging, prevents lens fogging of eyeglasses worn under the goggle, and avoids audible noises from a fan used to prevent lens fogging.
1.2. Background Art
Modern ski goggles attempt to achieve a number of design goals dictated by operation in a harsh winter environment. These design goals include attenuation of bright outside visible light, elimination of ultraviolet solar radiation, maximizing visual recognition of snow pack features in both high and low light levels, prevention of goggle lens fogging, prevention of fogging of eyeglasses worn under a goggle, and exclusion of various other outside harsh weather environments. These goals need to be achieved via means which do not generally impede motion of a skier, which do not detract from positive aspects of the skiing environment, and which can be offered commercially at reasonable prices.
Modern ski goggles, as are widely available commercially and as are further described in the prior art (see U.S. Pat. Nos. 3,377,626 to Smith and 4,150,443 to McNeilly) employ a design compromise characterized by over ventilation when a skier is in motion and under ventilation when the skier is at rest. This over ventilation results in uncomfortable wind chill effects on the skier's face and eyes, rapid temperature decrease of goggle and eyeglass lenses, and lens fogging when the skier's exhaled breath enters the goggle air space. When the skier comes to rest after vigorous skiing activity, under ventilation causes the dew point of the goggle air space to rise rapidly via expiration of water vapor from the skier's eyes, and intake of skier's exhaled breath. This elevated dew point, if it exceeds the decreased lens temperature, results in lens fogging.
A number of techniques are known in the art which minimize or eliminate such ski eyewear fogging. U.S. Pat. No. 2,526,737 to Farina discloses the use of a breath powered exhaust fan; Smith discloses an insulated goggle lens; McNeilly and U.S. Pat. No. 3,825,953 to Hunter disclose the use of an electric fan; U.S. Pat. No. 4,868,929 to Curcio discloses an electrically heated goggle lens; U.S. Ser. No. 07/947,740, filed by Ryden, the applicant herein, discloses electrically heated eyeglasses.
Farina discloses use of exhaust fans to remove moist air from the goggle space in front of the eyes. The shaft of this fan is shared with a turbine which is made to rotate by constraining the exhaled skier's breath to flow through the turbine and thereby rotate the fan shaft. This fan means is quite inconvenient to use on a continuous basis and is also impractical for operation at predetermined fan speeds. Furthermore, Farina does not address the use of eyeglasses under a goggle.
Smith discloses a multi-component lens goggle to increase the temperature of the innermost lens. This practice reduces goggle lens fogging, but is ineffective in preventing fogging of an eyeglass worn under a goggle. Smith also discloses an improved ski goggle that uses an air permeable goggle frame, so that the goggle air space is in slow but controlled air exchange with the outside air, thereby keeping the air inside the goggle and the skier's face warm but also preventing moisture accumulation. It is readily understood that such an air permeable frame may be advantageous over an open frame, such as that of an eyeglass; and advantageous over a closed frame that would allow moisture accumulation. Such an air permeable frame shows significant goggle air space temperature variation depending on the rate of skier motion. Use of an eyeglass under such a goggle will result in eyeglass lens fogging due to this temperature variation and intake of exhaled skier breath through the air permeable frame.
McNeilly and Hunter are both effective at preventing goggle fogging and McNeilly specifically discloses features intended to defog an eyeglass worn under a goggle. McNeilly relies on open goggle ventilation as disclosed by Smith for effective defogging of the McNeilly goggle. Consequently, McNeilly suffers from the over ventilation problem discussed above. Additionally, the electric fans used in both McNeilly and Hunter produce sound levels which are very annoying to the skier and, consequently, in practice, the fans are only operated to defog lenses as opposed to preventing fogging from occurring. This annoying sound level (estimated at 35 decibels) is due to the high fan blade rotational speed required to produce the desired defogging effect when using small fans of the type appropriate for mounting on or near a goggle.
Three examples of the usage of fans in ski goggles are commercially available. One of these is manufactured by Smith Sport Optics, Inc., assignee of the McNeilly patent. The other two examples are sold under the trademarks Uvex (Germany) and Swans (Japan) respectively. All of these commercial goggles exhibit the annoying sound level of McNeilly.
Electrical heating of goggles as practiced by Curcio or electrical heating of eyeglasses as practiced by Ryden are effective in preventing fogging. Ryden is silent in operation, and provides fog-free vision for eyeglasses with or without the use of goggles. A disadvantage of Ryden is that effective lens heating under a goggle requires about one watt of electrical power, and this level of power consumption for a full day of winter sports activity necessitates the use of a battery pack which is not comfortably mountable on the eyeglass or goggle.
While the methods disclosed in the prior art are effective in reducing or preventing fogging of winter sports eyewear, each has one or more deficiencies which detract from fully satisfactory use to achieve their intended defogging function. Accordingly, there is a need for an improved ski goggle which prevents goggle lens fogging and eyeglass lens fogging when worn under the improved goggle. Operation of the defogging means should be undetectable by the skier and self-contained on the goggle. Additionally, an improved ski goggle needs to provide a uniform level of comfort to the skier's face and eyes, irrespective of whether the skier is in rapid motion.